1. Field of the Invention
The present invention relates to recording means and an apparatus having said recording means, for forming an image by discharging liquid droplets onto the recording medium in accordance with image information, and more particularly to a recording head and an ink jet recording apparatus having said recording head, using heat generating elements as the energy generator in order to discharge liquid droplets.
2. Related Background Art
Conventionally, in the ink jet recording apparatus, the provision of a mechanism for detecting the ink remain within an ink storage portion has been proposed to prevent the ink within the ink storage portion from being completely exhausted on the course of the continuous scanning for recording, resulting in a failure (undischarge) of discharging no ink in accordance with the recording signal.
This ink remain detecting mechanism was typically in the form of reading the resistance value between two electrodes disposed at a fixed interval in an ink tank unit for holding the recording ink as shown in FIG. 1. This mechanism is one which detects whether or not the ink remains within the ink tank, using the variations in resistance value which resulted from the difference in specific resistance between the ink and the air.
In FIG. 1, 11 is an ink tank for holding the ink inside thereof, and 12 is a recording head for discharging the ink. This recording head 12 is internally provided with orifices for discharging recording liquid droplets, heaters which are heat generating elements for forming recording liquid droplets, and a plurality of ink flow passageways for supplying the ink to the regions where these heaters are provided, and is further formed with a common liquid chamber for supplying the ink to the plurality of ink flow passageways.
And 13 is a pair of electrodes for measuring the resistance value for detecting the ink remain within the ink tank 11, as above described. These electrodes are provided on the lower part of the ink storage portion within the ink tank, when mounted on the ink jet recording apparatus.
In the above constitution, the resistance between electrodes 13 becomes lower when there is plenty of ink inside, because the electricity will conduct, that is, the specific resistance of the ink is lower than that of the air, whereas when there is less ink inside than reaching the level where the electrodes are provided,
It becomes high. By sensing a change in this resistance value, the detection of whether or not the ink remains can be effected.
However, because the ink within the ink storage portion will oscillate along with the scanning for recording, at least one pair of electrode pins having a certain length must be provided within the ink storage portion to measure the resistance between the electrodes without malfunction, which imposed some restrictions on the shape of the ink storage portion.
Further, it is necessary that they are spaced away a predetermined distance from the wall of the ink storage portion or each other not to enable the electrical conduction due to ink liquid droplets sticking to the electrodes. Therefore, the detection will occur in the condition where there is still ink remain within the ink storage portion, for which an additional process including the pulse count is required to consume this remaining ink.
Also, even if the ink remain is detected to be sufficient, there is a possibility that because of bubbles incidentally arising around the common liquid chamber or ink flow passageways, as previously described, some of the ink flow passageways have been disconnected, wherein the detection of undischarge was not allowed.